The development of the laser and related light stimulative technology has generated a significant interest on the part of investigators in that branch of interferometry known as holography. In its underlying concept, holography generally considers that the scattering pattern of light from an object is a transform, or coded record, of the features of that object. Where such a scattering pattern is stored, for example, photographically, an image of the object should be reconstructable. Prior to the availability of an intense coherent light source, a required recordation of such patterns proved most difficult. However, with the availability of the laser as an intense coherent light source and with an innovation wherein the scattering pattern was combined to interfere with a reference beam of coherent light, a photographic wave-front reconstruction was realized. With the interference of reference and reflective subject beams, resultant interference fringes exhibited a recordable contract representing a measure of amplitude of the subject beam and the position of these fringes represented a recordable measure of phase of the subject beam. Where a photograph of such an interference pattern is illuminated with a laser beam identical with the original reference beam, diffracted light from the photograph will have the same amplitude and phase characteristics as the original beam from the subject.
The most interesting aspect of the holographic reconstruction resides in the very detailed and three-dimensional nature of a resultant image. Additionally, holograms have been found useful in the evaluation of stress exerted upon structural components. The three-dimensional resolution of motion pitcure holograms has been found helpful in studying microscopic life such as plankton. Holographically produced lenses have found use in aircraft windshield displays, while holographic scanners are used in retail price code scanning assemblies.
For each of the above and other applications, the holographic information storage is photographic in nature and, thus, somewhat limiting in application. However, the relatively large amount of imaging data available in a holographic image record should find extensive application within a broad range of developing technologies. In particular, a significant extension of holographic applications will occur where such records become the subject of electronic storage. Further, where electronic wave-front reconstruction is available, an advantageous holographic imaging and transmission in real time may be achieved. However, many obstacles are posed before the investigator seeking to record holographic data electronically. Questions arise as to whether a form of electronic sampling at a holographic reception surface can achieve adequate image resolution, notwithstanding the apparent complexity of any sampling procedure itself. Assuming that such sampling is to be carried out within discrete sampling regions of minute area, then some form of electronic detection is required which responds accurately to the extent of wavefront interaction or the intensity thereof and the resultant datum then must be transmissible in conjunction with positional logic. Current and contemplated phototransistor structures do not appear to represent a logical approach to the detection, isolation and transmission of holographic wavefront interactions.